Meter testing switch



Sept 8, 1931. w. H. SCHRAMM METER TESTING SWITCH Filed Jan. 25, 1928 o 4.Elllllllillllllllllllll '.Ullllllllllllllllllll AT'TORNEY PatentedSlept'. 8:, 19.31'

UNITED STATES PATENT OFFICE WALTER H. SCI-IRAMM, F PITTSBURGH,PENNSYLVANIA, ASSIGNOR T0 WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY,A CORPORATION OF PENNSYLVANIA METER TESTING SWITCH Application ledJanuary 25, 1928.

My invention relates to testing switches and particularly tometer-testing switches wherein testing terminals are provided forreceiving meter-test connections and whereby the test coils of a testmeter may be properly connected to a circuitl containing a standardmeter.

An object of my invention is to provide a test switch wherein theoperating handle cannot be moved to open position to interrupt thecircuitl except when all of the test connections have been yproperlyconnected to the test terminals within the switch.

A further object of my invention is to provde a meter-testing switchwherein the testing connections are latched in engagement with the testterminals and may be released by movement ofthe operating handle.

A further object of my invention is to provide a meter-testing switchthat may be attached to a switchboard panelwith a minimum of effort andwhich is compact and durable in construction.

A further object of my invention is to provide a meter-testing switchwith a housing having removable side walls to facilitate inspection andrepair of the switch without necessitating removal from the switchboardand wherein the operating handle is removably attached to the operatingrod within the switch so that it may be removed to prevent unauthorizedpersons from operating the switch.

These and other objects that will be made apparent throughout thefurther description of my invention, are attained by means of thetesting switch hereinafter described and illustrated in the accompanyingdrawings wherein, i

Figure 1 is a longitudinal section through a meter-testing switchembodying features of my invention.

Fig. 2 is a longitudinal section through the switch taken on the line11-11 of Fig. 1.

Fig. 3 is a transverse section of the switch taken on the line 111-111of Fig. 2,

Fig. 4 is a bottom plan view of the switch, showing its connection to aswitchboard panel, and

Serial No. 249,379.

Fig. 5 is a side elevation of the operating rod and the switch carrierblock.

Referring to the drawings, the device includes an insulating housing 5having a pair of integral guides 6 extending longitudinally thereof fromthe bottom 7 of the housing toward the outer end thereof. The guidesserve to support and guide a switch-bladecarrier block 8 which isprovided with grooves 9 for engaging the guides 6 and permittingreciprocation of the block within the housing. The block is provided, onopposite sides, with the switch contact blades 11 of the double typewhich yieldingly engage stationary contact blades 12 that are integralwith the terminal straps 13 which are secured, at their inner ends, toterminal studs 14C which project eXteriorly of the housing 5 and arethreaded to receive terminal clamping nuts 15.

The housing is provided with an insulating cover 16 that is attached tothe housing by means of screws 17 which are threaded into a met-alinsert rod 18 embedded in the insulating housing. The cover is providedwith four triangular openings 19 that register with the conductorterminal straps 13 for receiving test-connection terminals 21 indicatedby broken lines in Fig. l, and which are made triangular in crosssection so that they can be inserted in the openings 19 in onepredetermined position only.

The carrier block 8 is actuated by means of an operating rod 22 to whichan operating handle 23, having a threaded stud 24, is attached. The rod22 is connected to the block 8 by means of a threaded bolt 25 thatextends through an opening 26 in the block andA provides a lost-motionconnection between the operating` rod 22 and the switchblade carrierblock 8.

A helical spring 20 surrounds the bolt 25 and is disposed between theinner end of the recess 26 in the block S and a washer 27 on the bolt25. The spring 20 serves to yieldingly retain the switch carrier blockin a predetermined position with respect to the operating rod 22 and,when the operating rod 22 is in the closed position shown in Fig.

1, the spring retains the carrier block in such position that the switchblades 11 engage the contact members 12 and establishes a circuitconnection between a pair of the terminal studs 14.

It is an object of my invention to provide means for preventing openingmovement of the switch blades except when all of the test connectionsare in operative engagement with their respective conductor terminalstraps 13. For this purpose, the cover V16 is provided with two pairs ofclamping latches 28 that are pivoted on shafts 29 mounted on lugs 31that are integral with the cover 16. The clamp latches are provided withprojections 32 that are adapted to engage in notches 33 in thetest-connection terminals 21 which are triangular in crosssection. Theclamps are biased into engagement with the connection terminals by meansof spring 34 disposed on opposite sides of the rod 22 to engage theinner ends of the clamp latches 28, as indicated in Fig. 1.

The outer ends of the latches 28 are provided with shoulder pins 35 thatengage shoulders 3G on the clamp rod 22 and prevent inward movementthereof so long as the latches are in the positions indicated in fulllines in Fig. 1. However, when the testconnection terminals 21 areinserted so that they engage the outer ends of the conductor strapterminals 13, as indicated in broken lines in Fig. 1, the latches 28 aredisplaced so that the pins 35 no longer engage the shoulders 36. Theoperating rod 22 may then be forced inwardly by pushing on the handle23, thus moving the switch blades 11 out of engagement with the contactterminals 12. By reason of this arrangement of latches it is necessaryto insert all four testconnection terminals 21 before the switch may bereleased and moved to open position.

When it is desired to detach the test-connection terminals 21, it isfirst necessary to retract the clamp latches 28 from engagement with thetest-connection terminals. It will be noted that the operating rod 22 isprovided with a pair of oppositely disposed inclined cam faces 37 whichare engaged by the pins 35 when the operating rod 22 is withdrawn beyondthe closed position, as shown in Fig. 1. This movement causes outwardmovement of the outer ends of the clamp latches 28 and withdraws theprojecttions 32 of the latches out of the notches 33 in thetest-connection terminals 21. The switch is closed at this time and,therefore, the test-connection terminals may be withdrawn withoutinterrupting the normal circuit through the test switch. After theconnection terminals are released, the rod 22 is permitted to return,under the influence of the spring 20, to the normal position shown inFig. 1. In operation, the test switch is connected in a load circuit insuch manner that current normally iows through both of the switch blades11. Opening operation of the switch is precluded by engagement of thepins 35 of latches 28 with the shoulders 36 on the rod 22. When all fourtest-connection terminals have been properly placed in engagement withthe terminals 13, the latches 28 are retracted to permit the operatingblades 23 to be pushed inward to disengage the switch blades 11 from thecontact jaws 12.

The test-connection terminals 21 cannot be removed until the switchblades are moved to closed position and the handle 23 drawn outward tocause releasing movement of the latches 28, by reason of the engagementof the rollers 35 with the inclined surfaces 37 on the rod 22.Therefore, the circuit through the blades 11 must be closed before thetest connections can be removed.

While I have illustrated but one embodiment of my invention, it will beapparent to those skilled in the art that various changes,modifications, substitutions, additions and omission may be made in theapparatus illustrated Without departing from the spirit and scope of myinvention as set forth in the appended claims.

I claim as my invention:

1. The combination with a testing switch having a movable contact forcontrolling a circuit and operating means therefor, of a test clipinterlocked with the operating means for re easably receiving testterminals for shunting the movable Contact and for preventing operationof the contact except when the test terminals are in operative relationto the said clip.

2. The combination with a testing switch having a switch contact movableto open and closed positions, and means for yieldingly retaining theswitch contact in closed position, of a terminal for receiving a testconnection, and a latch for preventing opening movement of the switchcontact operable by the test connection and yieldingly retaining theconnection in operative position.

3. A testing switch comprising a. movable switch contact, an operatingmember having a lost-motion connection thereto, a test terminal forreceiving a test connection, a latch for yieldingly retaining theconnection in operative position and for preventing opening movement ofthe operating member and operable by the test connection to release theoperating member to permit opening movement thereof.

4. The combination with a testing switch having a movable contact, anoperating means therefor and a plurality of test terminals for receivingtest connections, of means for yieldingly retaining the connections inoperative positions and for preventing operation of the said contactexcept when all of the hast comnections are in operative connection withtheir respective test terminals.

5. A testing switch comprising a casing, a switch contact member guidedfor movement therein within predetermined limits, a contact memberengaged by the switch contact member when the latter is in one of itslimited positions, a test terminal, an operating member having alost-motion connect-ion to the switch contact, means for releasablyretaining the operating member in a fixed position and for releasablyholding a test connection, yielding means connected to the operatingmember and the switch contact for yieldingly retaining the switchcontact in the said limited position, and means actuated by theoperating means for releasing the retaining means.

6. A testing switch comprising a pair of contacts having test terminalsadapted to be engaged respectively by test conductors, a bridging switchcontact member for conductively connecting the said contacts, a testclip for each test terminal for releasably engaging a test conductor andretaining it in contact with its respective test terminal, the saidclips normally engaging the said member and preventing opening movementthereoi and being displaced by the test conductors to permit openingmovement of the member only when the test conductors are in operativeposition.

In testimony whereof, I have hereunto subscribed my name this 23rd dayof January WALTER H. SCHRAMM.

